The present invention relates to a mechanical fastener and method for making the same. The present invention relates more particularly to a mechanical fastener including engaging stems having heads with demarcation lines. The present invention also relates more particularly to a method of making a mechanical fastener which includes placing a layer of heated material on stem ends to soften the stems ends and deforming the softened stem ends into convex heads.
Various types of mechanical fasteners arc known for holding articles together, such as hook and loop type fasteners or complementary pairs of fasteners that engage with one another. The complementary pairs of fasteners typically have engaging surfaces with patterns of stems having heads. Various methods have been used to head the stems of these fasteners. For example, U.S. Pat. No. 5,077,870, xe2x80x9cMushroom-Type Hook Strip for a Mechanical Fastener,xe2x80x9d (Melbye et al.), describes a method for forming mushrooms on an array of upstanding stems. A web having an array of upstanding stems made of thermoplastic resin is fed between two calendar rolls. The roll that contacts the stems heats the tips of the stems to a temperature exceeding the flow point of the thermoplastic resin. Briefly, maintaining the tips at this temperature allows molecular disorientation to take place. During this time and upon subsequent cooling, the tips draw back to form uniformly shaped mushroom heads, each having an upper, substantially convex surface and a larger cross section that the original stem.
PCT publication WO 98/57564, xe2x80x9cMethod and Apparatus for Forming Headed Stem Mechanical Fastener Structure, (Kampfer), published on Dec. 23, 1998, describes a method of deforming the hook head portions of hook elements on a web backing. The hook elements on the web backing are fed into a nip formed between a support surface and an upper heated surface having a durameter hardness of less than 90 Shore A. This upper heated surface compressively engages the hook head causing it to turn down and permanently deform. This increases the uniformity of the hook head elements forming a fiber engaging crook region.
One aspect of the present invention provides a mechanical fastener. The mechanical fastener comprises a substrate including a first major surface; and a plurality of engaging stems extending from the first major surface of the substrate, where each of the engaging stems includes a convex head, and where each of the heads includes a demarcation line.
In one preferred embodiment of the above fastener, the demarcation lines are generally parallel to one another. In another aspect of this embodiment, the demarcation lines are generally parallel to the first major surface of the substrate. In another preferred embodiment, each of the heads includes an outermost periphery, and the demarcation line is located on the outermost periphery. In another aspect of this embodiment, the periphery is generally circular.
In another preferred embodiment of the above fastener, the plurality of engaging stems comprise polymeric material. In another aspect of this embodiment, the polymeric material comprises a thermoplastic material. In another aspect of this embodiment, the thermoplastic material comprises a polyolefin. In yet another aspect of this embodiment, the polyolefin comprises polypropylene. In yet another preferred embodiment of the above fastener, the substrate and the plurality of engaging stems are integrally formed. In another preferred embodiment of the above fastener, the fastener is an interengaging mechanical fastener. In yet another preferred embodiment of the above fastener, the engaging stem includes a height of 0.005 to 0.2 inches measured from the first major surface of the substrate to the top of the convex head.
Another aspect of the present invention provides a method of forming a mechanical fastener. The method of forming the mechanical fastener comprises the steps of: a) providing a substrate including a first major surface and a plurality of stems extending from the first major surface of the substrate, where each of the plurality of stems includes a stem end; b) placing a layer of heated material on the stem ends to soften the stem ends; and c) deforming the softened stem ends into convex heads.
In a preferred embodiment of the above method, step c) includes compressing the layer of heated material and substrate to deform the softened stem ends into convex heads. In another aspect of this embodiment, step c) further comprises compressing the layer of heated material and the substrate between a nip formed between a first roller and a second roller, where the first roller contacts the substrate opposite the first major surface, and where the second roller contacts the layer of heated material. In another preferred embodiment of the above method, the method further includes the step of: d) stripping the layer of material from the plurality of convex heads. In another aspect of this embodiment, the method further includes the step of cooling the layer of heated material prior to step d).
In another preferred embodiment of the above method, the method further comprises imparting a demarcation line on each of the convex heads. In another aspect of this embodiment, the convex head includes a first portion that contacts the layer of heated material and a second portion that does not contact the layer of heated material, and where the demarcation line on the convex head is at a boundary formed between the first portion and the second portion of the convex head. In another aspect of this embodiment, the method further includes the step of forming a plurality of depressions in the layer of heated material where the layer of heated material contacts the first portion of the convex heads. In yet another preferred embodiment of the above method, step c) comprises deforming the softened stem ends around the plurality of stems to form a plurality of convex heads. In another preferred embodiment of the above method, step b) comprises extruding a layer of material on the stem ends.
In another preferred embodiment of the above method, the layer of material comprises polymeric material. In another aspect of this embodiment, the polymeric material comprises a thermoplastic material. In another aspect of this embodiment, the thermoplastic material comprises a polyolefin. In yet another aspect of this embodiment, the polyolefin comprises polypropylene. In another aspect of this embodiment, the polyolefin comprises polyethylene.
In another preferred embodiment of the above method, the plurality of engaging stems and the convex heads comprise a polymeric material. In another aspect of this embodiment, the polymeric material is a thermoplastic material. In another aspect of this embodiment, the thermoplastic material is a polyolefin. In yet another aspect of this embodiment, the polyolefin comprises polypropylene.
Another aspect of the present invention provides an alternative mechanical fastener. The mechanical fastener comprises a substrate including a first major surface; and b) a plurality of engaging stems extending from the first major surface of the substrate, where each of the engaging stems includes a base attached to the first major surface of the substrate and a tip opposite the base, where each of the engaging stems includes a convex head attached to the tip of the engaging stem, where the convex head includes a lobe adjacent the engaging stem creating a mutual wall between the lobe and the tip of the engaging stem. In a preferred embodiment of this fastener, the mutual wall is at least 5% of the height of the convex head measured from the bottom of the lobe to the top of the convex head.
Another aspect of the present invention provides a composite article. The composite article comprises a) a substrate including a first major surface; and b) a plurality of stems extending from the first major surface of the substrate, c) a layer of material including a first major surface, where the first major surface of the layer of material is melt bonded to the plurality of stems. In a preferred embodiment of the composite article, each of the stems includes a convex head, and each of the heads includes a demarcation line. In another aspect of this embodiment, the convex head includes a first portion that contacts the layer of material and a second portion that does not contact the layer of material, and the demarcation line on the convex head is at a boundary formed between the first portion and the second portion of the convex head. In another aspect of this embodiment, each of the heads includes an outermost periphery, and the demarcation line is located on the outermost periphery.
In another preferred embodiment of the above composite article, the layer of material comprises polymeric material. In another preferred embodiment of the above composite article, the substrate and the plurality of engaging stems are integrally formed. In yet another preferred embodiment of the above composite article, the plurality of engaging stems comprise polymeric material.
Another aspect of the present invention provides an alternative mechanical fastener. This mechanical fastener comprises: a) a substrate including a first major surface; and b) a plurality of engaging ribs extending from the first major surface of the substrate, where each of the ribs includes a convex ridge opposite the substrate, and where each of the convex ridges includes a demarcation line. In a preferred embodiment of this mechanical fastener, each of the convex ridges includes two demarcation lines along the length of each convex ridge. In another aspect of this embodiment, each of the convex ridges includes two demarcation lines located at the widest portion of the convex ridge opposite each other.
In another preferred embodiment of the above mechanical fastener, the demarcation lines are generally parallel to one another. In another aspect of this embodiment, the demarcation lines are generally parallel to the first major surface of the substrate. In another preferred embodiment of the above fastener, the substrate and the plurality of engaging ribs are integrally formed. In another preferred embodiment of the above fastener, the fastener is an interengaging mechanical fastener. In yet another preferred embodiment of the above fastener, the plurality of engaging ribs comprise polymeric material.
Another aspect of the present invention provides a method of forming a mechanical fastener. The method of forming a mechanical fastener comprises the steps of: a) providing a substrate including a first major surface and a plurality of ribs extending from the first major surface of the substrate, where each of the plurality of ribs includes a rib end; b) placing a layer of heated material on the rib ends to soften the rib ends; and c) deforming the softened rib ends into convex ridges.
In a preferred embodiment of the above method, step c) includes compressing the layer of heated material and substrate to deform the softened rib ends into convex ridges. In another aspect of this embodiment, step c) further comprises compressing the layer of heated material and the substrate between a nip formed between a first roller and a second roller, where the first roller contacts the substrate opposite the first major surface, and where the second roller contacts the layer of heated material.
In a preferred embodiment of the above method, the method further comprises the step of: d) stripping the layer of material from the plurality of convex ridges. In another aspect of this embodiment, the method further comprises the step of cooling the layer of heated material prior to step d). In another preferred embodiment of the above method, the method further comprises imparting a demarcation line on each of the convex ridges. In yet another preferred embodiment of the above method, step b) comprises extruding a layer of material on the rib ends.
Another aspect of the present invention provides an alternative mechanical fastener. This mechanical fastener comprises: a) a substrate including a first major surface; and b) a plurality of engaging stems extending from the first major surface of the substrate, where each of the engaging stems includes a convex head, where each of the convex heads includes a first portion at the top of the head and a second portion at the bottom of the head, and where the first portion of the head is smoother than the second portion of the head.
In a preferred embodiment of the above fastener, each of the heads includes a demarcation line and where the demarcation line is the boundary between the first portion of the head and the second portion of the head. In another aspect of this embodiment, the demarcation lines are generally parallel to one another.
In another preferred embodiment of the above fastener, each of the heads includes an outermost periphery, and where the demarcation line is located on the outermost periphery. In another preferred embodiment of the above fastener, the plurality of engaging stems comprise polymeric material. In another aspect of this embodiment, the polymeric material comprises a thermoplastic material. In yet another aspect of this embodiment, the thermoplastic material comprises a polyolefin. In another aspect of this embodiment, the polyolefin comprises polypropylene. In another preferred embodiment of the above fastener, the substrate and the plurality of engaging stems are integrally formed. In yet another preferred embodiment of the above fastener, the fastener is an interengaging mechanical fastener.